Fix last_response_json() to work with 'application/problem+json'

[cgiachalis]

closes #782

library(plumber2)
library(httr2)

api <-  api() |>
  api_get(
    "/health",
    function() {
      plumber2::abort_bad_request("bad request")
    }
  )

mirai::daemons(1)

# run api in a separate process & do not block the current process
mi <- mirai::mirai({
  api$ignite(block = TRUE, showcase = FALSE)
}, api = api)


request("http://127.0.0.1:8080/health") |>  req_perform()

# Error in `req_perform()`:
# ! HTTP 400 Bad Request.

 last_response_json()
{
  "type": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.1",
  "title": "Bad Request",
  "status": 400,
  "detail": "bad request"
}

[hadley]

I'm pretty sure there's some existing suffix parsing code that you could use to determine if there's a +json suffix. (I might be misremembering, but I think it's more generic than just application/problem)

[cgiachalis]

Do you want me to replace

httr2/R/last.R

Lines 64 to 66 in c7d4a86

	if (!identical(resp_content_type(resp), "application/json")) {
	cli::cli_abort("Last response doesn't have a JSON body.")
	}

with

  resp_check_content_type(
    resp,
    valid_types = "application/json",
    valid_suffix = "json",
    check_type = TRUE
  )

# or 

check_content_type(
    resp_content_type(resp),
    valid_types = "application/json",
    valid_suffix = "json",
    inform_check_type = TRUE
)

?

Example:

library(httr2)

req_perform(request(httr2:::example_url("/xml")))
#> <httr2_response>
#> GET http://127.0.0.1:57838/xml
#> Status: 200 OK
#> Content-Type: application/xml
#> Body: In memory (610 bytes)
resp <- last_response()

# last_response_json() will use
httr2:::check_content_type(
  resp_content_type(resp),
  valid_types = "application/json",
  valid_suffix = "json",
  inform_check_type = TRUE
)
#> Error:
#> ! Unexpected content type "application/xml".
#> • Expecting type "application/json" or suffix "json".

^{Created on 2026-01-14 with reprex v2.1.1}

[hadley]

Yes, that sounds great

[hadley]

Looks good! Can you please also add a news bullet to the top of NEWS.md? It should briefly describe the change and end with (@yourname, #issuenumber).